Dr Buqing Yao tells us more about his recently accepted paper titled ‘Ecosystem nitrogen retention is regulated by plant community trait interactions with nutrient status in an alpine meadow‘.
Ecosystem nitrogen retention is a crucial function that underpins productivity and ecological processes. However, there is currently no scientific consensus as to the key ecological factors controlling terrestrial ecosystem N retention (De Vries & Bardgett, 2012).
Nutrient availability is recognized as being a universal driver of community structure and function (LeBauer & Treseder 2008; Vitousek et al. 2010), partly as a result of species level differences in resource utilization. We speculate therefore that the control factors on ecosystem N retention might change with changing soil nutrient concentrations by changing plant growth, the dominant plant group or traits that are associated with N retention.
In this investigation we conducted a 15N labelling experiment to test how plant community properties, including plant species richness/diversity, dominance and functional traits, influence plant N uptake and retention under different nutrient availabilities at the Haibei Alpine Meadow Ecosystem Research Station on the Tibet-Qinghai Plateau, an area which has been shown to be highly sensitive to anthropogenic activities and climate change (Shen et al. 2014).
Results show that the controls on alpine grassland ecosystem 15N retention changed with the addition of nutrients. Conservative plant traits, species richness and root biomass influenced N retention in low to medium soil N conditions, and exploitative plant traits became more important with increasing soil N availability.
Interestingly, this finding concurs with the characteristics of dominant plant species in plant communities at different successional stages: conservative plants and exploitative plants were the dominant species under soil N deficient and N abundant conditions, respectively, with the greatest species richness found in the middle soil N state in the alpine meadow (Zhou, Yao, & Yu 2016). Thus, we can conclude that the controls of ecosystem 15N retention were strongly affected by nutrient inputs and mediated by changes in plant community level traits that varied according to soil N status.
This new understanding of the interaction between community traits and nutrient biogeochemistry offers a mechanism by which to predict ecosystem N retention and consequent changes in vegetation in the vulnerable Alpine meadow ecosystems of the Qinghai-Tibet plateau.
Further works can be done to advance this topic, for example, the differences between the plants of conservative or exploitative in response to N availability might be valuable as it could be an important means to predict N retention in changing alpine meadow communities due to N deposition and climate change. Additionally, microbial competition for N could be an important part of the N retention, and furthermore, the interaction between plants and microbes (e.g. mycorrhizal vs non mycorrhizal, vs specialist root adaptations such as in the Cyperaceae) and how these influence microbial N uptake could be a very important part of the N retention story.
Buqing Yao, Northwest Institute of Plateau Biology, CAS, China